1. Field of the Invention
The present invention relates to an organic-inorganic metal hybrid material, and a composition for producing an organic insulator comprising the hybrid material.
2. Description of the Related Art
Most thin film transistors (TFTs) currently used in display devices consist of an amorphous silicon semiconductor, a silicon oxide insulating film and metal electrodes.
With the recent advances in various materials, organic TFTs using organic semiconductors have been developed (U.S. Pat. No. 5,347,144). Organic thin film transistors have been researched worldwide due to their applicability based on the new configuration. In particular, such organic thin film transistors have an economical advantage in that they can be fabricated by printing processes at ambient pressure, and further by roll-to-roll processes using plastic substrates, instead of conventional silicon processes, such as plasma-enhanced chemical vapor deposition (CVD).
Organic semiconductor materials for channel layers of organic thin film transistors are largely divided into low molecular weight materials or oligomers, e.g., melocyanine, phthalocyanine, perylene, pentacene, C60, thiophene oligomer, etc., and high molecular weight materials. Lucent Technologies Inc. and 3M Inc. developed devices with charge carrier mobilities as high as 3.2 ˜5.0 cm2/Vs using a pentacene single crystal (3M, Mat. Res. Soc. Sym. Proc. 2003, Vol. 771, L6.5.1˜L6.5.11). In addition, the companies reported a device having a relatively high charge carrier mobility of 0.01˜0.1 cm2/Vs (CNRS, J. Am. Chem. Soc., 1993, Vol. 115, pp. 8716˜9721) and Ion/Ioff ratio using an oligothiophene derivative. However, the fabrication of these devices is mainly dependent on vacuum processes for thin film formation.
A number of organic thin film transistors (OTFTs) fabricated using a thiophene-based polymer as a high molecular weight material are reported. Although high molecular weight materials have poor device characteristics when compared to low molecular weight materials, they are advantageous in terms of their easy processability allowing them to be processed in a large area at low costs by a solution process, such as printing. Cambridge University and Seiko Epson Corp. have already fabricated and tested high molecular weight-based organic thin film transistors (charge carrier mobility: 0.01˜0.02 cm2/Vs) employing a polythiophene-based material (F8T2) (see, PCT Publication WO 00/79617, Science, 2000, vol. 290, pp. 2132˜2126). Bao et al. from Lucent Technologies Inc. disclosed the fabrication of organic thin film transistors (charge carrier mobility: 0.01˜0.04 cm2/Vs) employing P3HT, which is a regioregular polymer (U.S. Pat. No. 6,107,117). As noted above, these organic thin film transistors using high molecular weight materials have poor TFT device characteristics, including charge carrier mobility, compared to organic thin film transistors using pentacene as a low molecular weight material, but do not require a high operating frequency, and thus can be fabricated at low costs.
Studies on materials for insulating films which can be processed by a solution process are required in order to fabricate flexible organic thin film transistors at reduced cost, like the aforementioned organic semiconductor materials for channel layers. Further, studies on materials for insulating films are actively being undertaken to improve the performance of organic thin film transistors. Particularly, in an attempt to decrease threshold voltage, insulators having a high dielectric constant, for example, ferroelectric insulators, such as BaxSr1-xTiO3 (barium strontium titanate (BST)), Ta2O5, Y2O3, TiO2, etc., and inorganic insulators, such as PbZrxTi1-xO3 (PZT), Bi4Ti3O12, BaMgF4, SrBi2(Ta1-xNbx)2O9, Ba(Zr1-xTix)O3 (BZT), BaTiO3, SrTiO3, Bi4Ti3O12, etc., have been used as materials for inorganic insulating films (U.S. Pat. No. 5,946,551; and Adv. Mater., 1999, Vol. 11, pp. 1372˜1375). However, these inorganic oxide materials do not have any significant advantages over conventional silicon materials in terms of processing.
As the application of OTFTs has been recently extended to not only LCD displays but also driving devices of flexible displays using an organic EL element, the OTFTs are required to have a charge carrier mobility of 10 cm2/V-sec. or higher. However, since the OTFTs comprise organic insulating films having a dielectric constant of about 3 to about 4, they require a high driving voltage (30˜50V) and a high threshold voltage (15˜20V).
In an attempt to increase the dielectric constant of organic insulating films, dispersion of nanometer-sized ferroelectric ceramic particles in an insulating polymer is described in U.S. Pat. No. 6,586,791. But, this patent has some problems that the ceramic particles adversely affect the formation of an organic active layer, thus decreasing charge carrier mobility or increasing leakage current. To solve such problems, an additional organic material having sufficient insulating properties should be used to form a dual structure with the insulating polymer. Thus, there is a need in the art to develop an organic insulator that shows high dielectric constant, superior insulating properties, and excellent processability for better arrangement of organic semiconductor materials.